Looking for some memorabilia to commemorate this week's historic inauguration of President Barack Obama? University of Michigan mechanical engineering professor John Hart has come up with a memento that's perfect in these days of downsizing: NANOBAMAS.

Each nanobama measures just 500 µm across—roughly the size of the period at the end of this sentence—making it the world's smallest presidential portrait. Each visage is made up of about 150 million carbon nanotubes, approximately one for each person who voted in the 2008 presidential election, Hart notes.

"I hoped to use the Obama image as a popular icon that would bring public interest to the topic of nanotechnology and, more broadly, to its applications and implications," Hart tells Newscripts. "Also, I thought 'nanobama' was a catchy name, and it would be fun to make the structures and photograph them."

Hart made the figures shortly before the election, and since early November, the nanobamas have succeeded in garnering media attention beyond magazines and websites for the scientifically inclined. They have even been spotted on the media and celebrity gossip blog gawker.com.

Although you can't actually buy the nanobamas—Hart says they're currently residing on a small section of a silicon wafer in his office—there's a description of how they're made along with plenty of neat pictures at nanobama.com.

Keeping the campaign promise he made to his daughters, Obama and his family will shortly welcome a new puppy to the White House, fulfilling a well-kept presidential tradition. According to the magazine mental_floss, only two presidents, Chester A. Arthur and Franklin Pierce, have left no record of a FIRST PET. Although presidents in recent memory have favored dogs and the occasional cat, mental_floss reminds us that the White House has been home to a menagerie of creatures.

Calvin Coolidge practically made the presidential residence into a zoo, complete with canaries, geese, a bobcat, lion cubs, a wallaby, and a bear. Coolidge was also the proud owner of Billy the pygmy hippopotamus, a gift from tire magnate Harvey Firestone.

At 6 feet long and more than 600 lb, it's entirely possibly that Firestone's "gift" was a convenient way of unloading a demanding pet. Billy eventually found a more suitable home at the Smithsonian National Zoo. If you've seen a pygmy hippo at an American zoo, chances are good that it's one of Billy's progeny.

John Quincy Adams' pet alligator was a gift from the Marquis de Lafayette. According to mental_floss, it lived in a bathroom in the East Room of the White House and was occasionally used to frighten guests.

Presidential pets to consider in these cost-conscious times include Pauline, the last cow to live at the White House, who made milk for William Taft, and the flock of sheep that Woodrow Wilson used as groundkeepers during World War I.